基于表面改性的泡沫铜池沸腾换热特性实验研究

论文总字数：32800字

摘 要

泡沫铜是一种新型的材料，它的特征是表面由金属骨架构成，这种骨架较为疏松，中间存在大量的间隙，因此是一种良好的多孔材料，在航空航天，电子热设计和能源动力领域都有着非常广泛的应用。表面润湿性作为泡沫铜的重要特征参数，对于池沸腾换热特性有着很深的影响。本文主要研究泡沫铜润湿性对池沸腾换热的影响，并提出一种超亲水表面上特定位置为超疏水性的泡沫铜表面，并观察其池沸腾换热特性。

论文首先制备具有极端润湿性表面的泡沫铜，研究其结构与表面润湿性的关系。随后观察极端润湿性表面水滴的行为，并分析了超亲水表面和超疏水表面水滴的不同现象，为制作混合润湿性表面做准备。

论文对超亲水性泡沫铜表面进行了局部改性处理，以获得具有混合极端润湿性的泡沫铜表面，其表面特征为在特定区域具有疏水性，在其余区域具有超亲水性。在此基础上，搭建了池沸腾实验台进行泡沫铜表面池沸腾换热特性实验。研究结果显示：孔隙较多、汽化核心多的优势使得泡沫铜在强化沸腾换热方面具有天然优势。但是泡沫铜内部复杂的骨架结构也会成为换热的障碍。所以，泡沫铜的换热有优有劣。泡沫铜的孔密度不同时，其内部汽化核心数也不同，PPI越大，汽化核心越多；但PPI越大，骨架结构越复杂，气泡剥离时受到的阻力也越大。本次实验中，50PPI的泡沫铜的换热性能好于130PPI的泡沫铜的换热性能。实验同样还研究了改性后的泡沫铜的换热性能，结果表明，在相同厚度，相同PPI的情况下，超亲水样品比超疏水样品的换热性能要好。超亲水样品亲水疏气，对气泡存在排挤力，能够强化换热；超疏水样品疏水亲气，汽化核心容易形成，对气泡的阻力较大，换热性能随着热流密度增大而减弱。实验还对混合润湿性泡沫铜的换热性能进行了研究，研究结果表明，混合润湿性表面在沸腾前期往往都能起到强化换热的作用，但在沸腾后期，其强化效果与疏水区域的位置选择、疏水区域的面积和泡沫铜PPI值的选择都有关系，合理的选择疏水区域的大小和位置，混合润湿性表面的换热性能会比超亲水材料更好。

关键词：泡沫铜；混合润湿性；池沸腾；传热强化

ABSTRACT

Copper foam is a new type of material. It is characterized by its surface composed of metal skeleton, which is loose and there are lots of gaps in the middle. So it is a good porous material. It has a very wide application in aerospace, electronic thermal design and energy power field. Surface wettability, as an important characteristic parameter of copper foam, has a profound effect on pool boiling heat transfer characteristics. In this paper, the effect of the wettability of copper foam on pool boiling heat transfer is studied. A super hydrophobic surface of copper foam on a super hydrophilic surface is proposed and its pool boiling heat transfer characteristics are observed.

In this paper, copper foam with extreme wetting surface was prepared and its surface microstructure was studied, and the relationship between its microstructure and surface wettability was studied. Subsequently, the behavior of water droplets on extreme wettability surface was observed, and the different phenomena of water droplets on superhydrophilic surface and superhydrophobic surface were analyzed to prepare for making mixed wettability surface.

In this paper, the mixed wettability surface was fabricated by cutting and welding, and the different phenomena between the surface and the superhydrophilic and superhydrophobic surface were observed. Experiments were carried out to prove that cutting and welding copper foam had little effect on the heat transfer characteristics of copper foam. On this basis, pool boiling experimental platform was set up to conduct pool boiling heat transfer experiments on copper foam. The results show that the advantages of more pores and more core of vaporization make the copper foam have a natural advantage in enhancing boiling heat transfer. However, the complicated internal skeleton structure of copper foam will also become an obstacle to heat transfer. Therefore, the heat exchange of copper foam is good and bad. When the density of copper foam is different, the number of inner vaporization cores is different. The larger the PPI, the more the core of vaporization. But the larger the PPI, the more complex the skeleton structure is, and the greater the resistance is. In this experiment, the heat transfer performance of 50PPI copper foam is better than that of 130PPI copper foam. The experiment also studied the heat transfer performance of modified copper foam. The results showed that the super hydrophilic sample had better heat transfer performance than the superhydrophobic sample at the same thickness and the same PPI. Super hydrophilic sample is hydrophilic and degassing, and has squeezing force on bubbles, which can enhance heat transfer. Super hydrophobic sample is hydrophobic and hydrophobic, and the vaporization core is easy to form. The resistance to bubbles is larger, and the heat transfer performance decreases with the increase of heat flux. The heat transfer performance of mixed wetting copper foam was also studied in the experiment. The results showed that the mixing wettability surface often played a role in enhancing heat transfer in the early stage of boiling. However, in the later stage of boiling, the enhancement effect was related to the location selection of hydrophobic region, the surface area of hydrophobic region and the choice of PPI value of copper foam, and the size and location of hydrophobic region were reasonably selected. The heat transfer performance of the mixed wettability surface is better than that of the superhydrophilic material.

KEY WORDS: copper foam; mixed wettability; pool boiling; heat transfer enhancement.

目 录

摘 要 I

ABSTRACT II

第一章 绪论 1

1.1研究背景及意义 1

1.2泡沫金属研究现状 2

1.2.1 超亲水材料的制备 2

1.2.2 超疏水材料的制备 2

1.2.3 混合润湿性表面的制备 3

1.2.4 泡沫金属 3

1.2.5 池沸腾 4

1.3 本文研究内容 4

第二章 泡沫铜混合润湿性的制备 5

2.1理论基础 5

2.1.1 表面张力和表面能理论 5

2.1.2 接触角及接触角理论 5

2.1.3 混合润湿性表面换热特性 6

2.2 实验内容 6

2.2.1 材料和试剂 6

2.2.2制作方法 6

2.2.3 验证方法 7

2.3实验结果 7

2.3.1 超亲水表面 7

2.3.2 超疏水表面 8

2.3.3 超亲水和超疏水混合表面 8

2.4 本章小结 12

第三章 池沸腾实验装置及方法 13

3.1实验装置设计 13

3.1.1 恒温控制 13

3.1.2 数据采集 13

3.1.3 加热系统 14

3.1.4 实验腔体 15

3.2实验块 16

3.2.1 热电偶加热棒连接方式 17

3.2.2 泡沫铜与铜块的连接 17

3.2.3 保温密封措施 18

3.3 实验步骤和方法 19

3.4 实验数据处理和误差分析 19

3.4.1 实验数据处理 19

剩余内容已隐藏，请支付后下载全文，论文总字数：32800字